Abstract: A screw press includes a ram, mounted for reciprocating movement relative to a press body, having a rotatably mounted threaded spindle extending therefrom, and a flywheel joined to the spindle for transmitting movement to the ram. The flywheel is driven by a friction disk which is arranged to engage the outer periphery of the flywheel, the disk being mounted on a shaft supported in the press body for rotational and axial movement relative to the body. When desired, the shaft can be axially moved to cause the disk to engage the flywheel, and an associated drive unit including a drive motor operates to rotatably drive the disk, thereby causing the ram to be moved within a work space in the press body. Preferably, one or more pairs of friction disks are arranged about the flywheel, each of the disks having an associated drive unit whereby the ram can be moved at different speeds and its direction reversed in accordance with the types of drive motors provided in the drive units.